510 



REPORT — 188-1. 



chloric acid also ; because, whatever effect the hydrogen affinity may have 

 in changing the numbers, it will have the same effect on all. 



It is easy to write down the hypothetical series in bromine and iodine in 

 the same way — 



Calculated Volta Series in Bromine and Iodine. 



All this supposes the metals to be perfectly clean, and not covered with 

 a film of foreign gas like oxygen. On the hypothesis that the metal has 

 been taken recently out of air, and that the film of oxygen with which it is 

 covered has to be torn from the metal, though it was not actually com- 

 bined with it, the Volta series in chlorine or hydrochloric acid would be 

 quite different, and more like this. 



Hypothetical Volta. Sen s of J r-c ' Metals in Chlorine of IICl. 



Silver .... is I Copper .... "9 

 ad 1"2 Zinc .... 



Iron 1*1 I 



Unfortunately I can get no data for the heat of chlorination of nickel, 

 but assuming it not very different from iron, the nbove series gives copper 

 and nickel in the right order, as observed by Mr. Brown, whereas the other 

 one did not. I have no experiments with which to compare the numbers. 



Calculated Volta Series of Clean Metal* in Sulphur or Sulphuretted 



Hydrogen. 



But it will be observed that this is nothing like the order to be ex- 

 pected in sulphuretted hydrogen ; for it is popularly known that copper 

 is more easily sulphurised in this gas than iron. Now assuming that the 

 metal had been covered with an air film, and that the oxygen of this has 

 to be replaced by sulphur, the chemical tendency, instead of being M,S, 

 is something more like M,S— M,0, or- possibly M,S — M,0 + H 2 ,0 — H 2 ,S ; 

 and either of these will give a quite different order. Data are given on 

 p. 624 of Naumann's ' Gmelin-Kraut,' vol. i., for the neutralisation heats 

 of various bases by H.,S, such as CuO + H 2 S, &c. These are something 

 like what we want, and from them we reckon the following : — 



